Data storage system



May 19, 1964 J. J. CONNOLLY ETAL 3,134,016

DATA STORAGE SYSTEM Original Filed June 20, 1951 8 Sheets-Sheet 1 LIIB MASTER SEEKER PULSE (GAP RESET) DATE DECODER EQU SEE SYNC. PULSE SYNC. PULSE COUNTER COUNTER FIG. 6 PER.

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AVAILABILITY INTEGRATED AVAILABILITY SIGNAL- (LAST DESIGNATED LEG) INVENTORS, JOHN J. CONNOLLY l HAROLD F.MAY BY EDWIN L. SCHMIDT ATTORNEY y 1964 J. J. CONNOLLY ETAL 3,134,016

DATA STORAGE SYSTEM Original Filed June 20. 1951 8 Sheets-Sheet 2 l9 sYNc. PuLsE CHANNELS "i 2 6 I a I a as TITTTTF-JTTTTI READ awRITE HEADS mati 5 4 3 a I HIIIIHIIIIIHHH FOR LEG INVFTORY RELAY s EcTo CHAIWELS, A -CHANNEL I F'ERS FOR O 2| FAMILY FOR EACH DAY S-RELAY P R l0 GANG RELAYS l RELAY FORX DAYs AND I RELAY FOR 2- DAYs I 4 l5 I r37 READ wRI'rE SYN Q Q PAJ- AMPLI- E PULSE PIER Q GATE 7 W- 1 AMPLIFIERS a DIsORIMINATORs /FIRST REV- RELEASE I ,5 38 I I I I I I I 33 7 JOINT ADDREs INVENTORY cohlggol SAIIIIWESIG SYIF .COUNT --65O L. I024 IT-. r I r ADDRESS INv.ADDREss LOCK I SAMPLING SHIFT J. ARA om----- STORAGE REGISTER {LOCK 645 41: 1 ,49 28 R s 40 \fiI-QPTIEI s DIGIT 1- GATED 0 s SETTER AMPLI RELAYS REGISTERS FIERS B\ "5 LTD cANcEL D ORDER BY AIsT. .L. s

COMPUTER 3 :3 SEE s52 63: 2 FIG 8. 7 8| 8 H1 M l\ 52 INVENTORY T 5 SAMPLING STORAGE h 64? DIsTRIBuTIvE A ELECTRONIC INVENTORS. ll vnREs STORAGE JOHN J. CONNOLLY HAROLD F- MAY F G 2 BY EDWIN L.SOHM|DT Maw ATTORNEY y 1964 J. J. CONNOLLY ETAL 3,134,016

DATA STORAGE SYSTEM Original Filed June 20, 1951 8 Sheets-Sheet 3 E II- E m L; oi

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? g INVENTORJ. 5 JOHN J. CONNOLLY HAROLD I". MAY 0) g B EDWIN L. SCHMIDT Y E AMI-v ATTORNEY May 19, 1964 J. J. CONNOLLY ETAL DATA STORAGE SYSTEM Original Filed June 20, 1951 FIG.5

8 Sheets-Sheet 4 RESET PULSE CIRCUIT 63l TO MATRIX 3O STORW25E 43 TART PULSE IROUIT 630 mom LcABLE [Q a o mu'mx 50: mo STORAGE 43 I STEPPING FROM i CAELE STOP SIGNAL CIRCUIT 632) 8 (LAST DESIGNATED LEG INVENTORJ'.

JOHN J. GONNOLLY HAROLD F. MAY EDWIN L. SCHMIDT ATTORNEY 1964 J. J. CONNOLLY ETAL DATA STORAGE SYSTEM Original Filed June 20. 1951 8 Sheets-Sheet 7 FIG. 8

JOHN J. CONNOLLY HAROLD F. MAY EDWIN L. SCHMIDT ATTORNEY y 19, 1954 J. J. CONNOLLY ETAL 3,134,016

DATA STORAGE SYSTEM Original Filed June 20, 1951 8 Sheets-Sheet 8 4- mxcn PA IR COUNTER 2 w A FIG. 9 H6. K)

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COMPARATOR men PAIR 'A' vt-a REGISTER-2 INVENTORS JOHN J. CONNOLLY HAROLD F. MAY EDWIN L. SCHMIDT M ATTORNEY 3,134,016 Patented May 19, 1964 3,134,016 DATA STORAGE SYSTEM John J. Connolly, Pacific Palisades, CaliL, Edwin L. Schmidt, Katonah, N.Y., and Harold F. May, Basking Ridge, N.J., assignors to The Teleregister Corporation, Stamford, Conn. Continuation of application Ser. No. 232,548, June 20, 1951. This application Feb. 2, 1960, Ser. No. 6,206 22 Claims. (Cl. 235152) This invention relates to inventory systems using rapidly accessible storage of inventory items. It is particularly adapted for use in connection with equipment which is required for meeting the demands of passenger transportation systems catering to customers who wish to make seat reservations in advance.

This application is a continuation of our application Serial No. 232,548, filed June 20, 1951, now abandoned.

In a copending application of Dale H. Nelson, Serial No. 42,356 dated August 4, 1948, now Patent No. 2,737,- 342, which was assigned to the assignee of the instant application, an inventory system was disclosed, the techniques of which are, to a certain extent, followed in the system herein described. The objects of that application and of this one are similar in many respects. However, the instant application is an improvement over anything heretofore known in regard to the betterment of access time for the readout of desired inventory data, also in the gaining of time for performing certain operations, such as to subtract a reservation from a previous inventory balance and to post a new balance for the seat or space inventory of a certain flight, or leg of a flight.

Another improvement which is disclosed in the instant application relates to facilities which are provided for making inquiries simultaneously as to a group of flights or a series of legs of such flights. In this connection the present system is well adapted to make use of the invention of Edwin L. Schmidt, Serial No. 161,681 filed May 12, 1950, now Patent No. 2,564,410 issued August 14, 1951, wherein there was disclosed an agents keyset and necessary equipment for making simultaneous inquiries as to storage of inventoried items regarding a number of different flights or legs of flights.

Our invention does not absolutely require the use of the Schmidt keyset aforementioned but, because of its ready adaptation, we intend to use it in connection with the instant invention. The detailed specification to follow will assume some familiarity with the details of the Schmidt keyset.

The primary object of our invention is to provide an inventory system of the type wherein inventory balances are maintained in a continuously accessible magnetic storage unit and wherein access to a desired group of inventory balances is rapidly obtained through an initial group selection which is followed automatically by a sequential scanning of different individual balances chosen by the initial group selection.

It is another object of our invention to provide an inventory system having numerous novel and advantageous features and having electronic equipment whereby any one of a number of different modes of operation may be performed in respect to the requirements of a passenger transport reservation system. Among such operations may be mentioned the extraction of multiple items of inventory statistics in order to respond to an inquiry and to give a prospective customer a choice of available flights on any one of which he could make a reservation. Such reservations or mere inquiries, may be made, according to our invention, by the transmission of signals over signalling circuits from diflerent control points to a single station where the storage of inventory balances is maintained and from which answer-back information may be transmitted.

Numerous other objects and advantages of our system will be brought out in the description to follow. This description is accompanied by drawings wherein:

FIGS. 1 and 2, when placed side by side, show a schematic circuit arrangement of components which are suitably coordinated for performing all the desired operations in respect to the maintenance of an inventory system of the type described;

FIG. 3 is a circuit diagram showing a preferred form of electronic matrix as used in certain portions of our system;

FIG. 4 is a circuit diagram showing details of a special form of electronic gate with lock;

FIG. 5 is a schematic diagram of a preferred form of counting ring which is operable as a sequence switch and is capable of selecting eight circuits sequentially or is otherwise operable to make skip selections for economy of time;

FIG. 6 is a block diagram showing components of a programming section of our system;

FIG. 7 is a circuit diagram showing relay controls for executing different types of orders;

FIG. 8 is a circuit diagram showing in detail a typical digital order stage of an electronic computer; and

FIGS. 9 to 14 illustrate how various of the circuit devices or sections thereof may be wired to provide standard assembly or sub-assembly units: FIG. 9 is a mixer pair; FIG. 10 shows a unit of a counting circuit; FIG. 11 is a gate unit; FIGS. 12 and 13 show comparator units; and FIG. 14 illustrates a digit register unit.

THE BASIC COMPONENTS OF THE SYSTEM As shown in FIGS. 1 and 2, the system includes a number of different agents sets 1 located at convenient points where customers Wants can be taken care of. There is also a master set 3 which is used for posting new inventories, as well as revised recordings of inventory item addresses, and for checking inventory balances. Another special set 2, called a control set, is used in the flight control tower to check inventory balances immediately prior to take-off of a plane. In addition to local keysets there are remote keysets 6 which are connectable through leased lines and a line connector 5 to a selected one of several local transceivers 4 having storage facilities such as a perforated tape or relays. Any keyset or transceiver placing a call for connection to the common equipment first operates a master seeker. If there is no busy condition of the common equipment, then it is seized by the station making the call, all others being locked out.

Each keyset is provided with a date-key section and with keys for designating the kind of order that is to be given to the inventory system. There are also lamps on the keyset for indicating different answers that may be given automatically in response to the manner of execution of the orders by the common equipment. One of these lamps marked CHK (for Check) indicates, for example, that a sale order has been executed and an adjusted inventory balance has been posted to give effect to the transaction. This lamp is also lit to indicate the successful completion of any order. Another lamp indicates rejection of the order when, for example, the inventory balance is less than the number of seats called for by a customer. This lamp is also indicative, when lit, of any failure of the equipment to complete an order, including technical failures and errors of keyset operation, as when the agent sets up a date on his date keys for which no inventory balances are recorded.

The keysets are also provided with facilities for using code-notched designation plates of the type described in the Schmidt application above mentioned. These plates are notched along different edges so that when they are inserted in a pocket in the keyset in one of four different ways they automatically select different groups of flight inventories or leg inventories to be searched for information or to be changed when sales or cancellations are re quired.

The magnetic storage unit is preferably a single constantly rotating drum 12 having its cylindrical surface coated with magnetic material. In close proximity to the cylindrical surface is an array of reading and writing, or recording heads which scan record channels of three different groups. One group 19 is for deriving synchronizing pulses of different frequencies based on the revolutions of the drum. Another group 13 comprises serially recorded codes for what we call inventory addresses. The reading of address codes enables different individual items of the inventory to be read out and to be written in at selected arcuate points around the record channels, as required for a changing inventory. As will be explained hereinafter in more detail, it is possible when putting through a single order from the agents set to inquire as to availability of as many as eight different flights (either the same or different flights) and also to make a sale or a cancellation in respect to any individual one or more of the eight different items. The third group of record channels 26 relates to the inventory items themselves. Each inventory balance is maintained by recording a binary number and, for requirements presently contemplated, this number can be within the range of 0 to 127. Therefore a seven-unit binary code is used. Each inventory balance is recorded at one arcuate position around the drum. That is to say, the recording is in parallel along seven different channels. This is in contrast with the recording of leg addresses, where the code for each address is serially arranged in a particular one of a number of dilferent channels.

An electronic computer of novel construction is in cluded in the system and this computer will be given a detailed description hereinafter in connection with an explanation of its peculiar functions and its capabilities. A feature of this computer is that it will accept at one instant input signals representing all the digits of two binary numbers and at the same time deliver the result of a computation involving such numbers. Thus, when an old inventory balance is read out of magnetic storage during some portion of a magnetic drum revolution, assuming that that balance is injected into the computer along with an item to be added or subtracted, the computation is made almost instantaneously and the result is held ready to be written back into the same place on a channel of the magnetic drum from which the old inventory balance was read out. The new balance is recorded during the very next revolution of the magnetic drum.

The remaining portions of the equipment, although numerous and although coordinated in a complex manner, will best be understood in the more detailed description to follow.

DIFFERENT TYPES OF ORDERS TO BE EXECUTED The equipment is designed to function in response to any one of ten different types of orders, as follows:

(1) Availability inquiry.This is a simple request for information with regard to as many as eight different flight or leg inventory balances, particularly as to whether or not they are equal to the demand as specified in a call. The execution of this type of order involves a two-revolution scanning cycle, repeated for each of the eight legs in a selected group. In the first revolution of the drum an inventory address is read out from a selected are of a selected recording channel on the drum, and the address is stored for finding the corresponding inventory balance record in some part of a selected inventory channel. The inventory balance item is found by this address during the second revolution and is at the same time injected into the computer. The number of seats wanted by the customer is instantly subtracted from the old balance and if the difference is not negative the answer-back signal CHK is given for lighting an appropriate leg-designating lamp on the agents keyset. If the difference is negative, than the RBI signal is indicated by failure to light the lamp.

The current inventory balances are not disturbed by the execution of an availability inquiry order, since the read-out process does not involve erasure.

The execution of an availability inquiry order covering eight leg inventories of a selected group within the period of 16 drum revolutions is what we call a function of Cycle 1." That is to say, during the process each odd numbered revolution of the drum is devoted to the readout of a leg address, and each even numbered revolution is devoted to the read-out of an inventory item balance. As will later be seen, other types of orders require five drum revolutions for each leg. Cycle I is then processed completely for as few or as many legs as may be involved; then Cycle II having three revolutions per leg is caused to be processed in immediate succession to Cycle I.

(2) Selling a seat rerervati0n.-In this operation the preliminary searches are made for leg addresses and inventory balances during Cycle 1. This cycle may be shortened, however, to cover only the number of legs involved in the customers reservation. Then follows the processing of Cycle II with respect to the same number of designated legs. The inventory leg addresses and inventory balances are again read out, the sequence for each leg now being one which involves three drum revolutions because the new inventory balance recording is timed to occur in the third revolution.

(3) Limited cancel 0rders.-This type of cancellation is permitted by a customer-serving agent only when there is an above-zero balance in the inventory for the particular flight or leg in question. The equipment automatically rejects a cancellation order if the balance is zero, for it then becomes necessary to refer the order to the master agent or other person takes care of a waiting list by ordinary clerical methods. Our system executes limited cancel. orders automatically whenever the inventory balance is 1 or greater. Cycle II processing is substantially the same as for making a sale, except that the computer is set to perform addition instead of subtraction.

(4) Unlimited cancel orders-These orders are executed only by placing the call from the master agents keyset 3. The operation is one which disregards the question of whether the current inventory balance stands at balance is 1 or greater. Cycle II processing is substanorder to record the new inventory balance resulting from the addition of the number of seats cancelled to the old balance. So each of the designated leg inventories is dealt with in three revolutions of Cycle II.

(5) Read-0m of an inventory baIance.--This order is one which can be originated only from the master keyset 3, since the indicating means for receiving the answerback signals are included only in the master agents set. Such means comprise an array of seven lamps (in the present embodiment of our invention) where each lamp corresponds with a different one of the binary digit orders of the inventory balance number. The read-out operation requires only the processing of Cycle I. The agents sets 1 are not equipped for indication of the exact inventory balances since all these agents need to know is what may be given them by the CHK and REJ signals.

(6) Writing new inventory balances-These orders are handled only from the master agents set 3. The operation is similar to order No. 4, as above described, with two exceptions: (1) the old inventory balance item does not enter the computer, and (2) the processing of this order is completed in Cycle 1.

(7) Read-out of inventory addresses.The recording of inventory addresses may at any time require verification. The read-out signals are stored in an address sampling register 50 in fulfillment of this order. The answerback means under control of the sampling register transmits signals to the master agents set where lamps are selectively lit to indicate the code pattern of the address. This order is executed in Cycle I.

(8) Write inventory addresres.-Whenever a change is needed with respect to the particular addresses to be included in a given group, new addresses may be recorded in any selected address channel. Signal transmitting means are provided in the master agents set 3 for doing this. The order is executed in Cycle I.

(9) Availability inquiry regarding a date beyond a ten day limit.-Inventories with numerical balances are maintained (according to our present embodiment of the invention) only for a ten day period. A new inventory record for the latest of the next ten days is entered in place of the record for the expiring day. For records of. availability beyond the 10day period a single channel is used to record a 1" or a O for showing the condition of a clerically maintained auxiliary inventory record. The magnetic record channel as used in this connection is referred to as covering X days. used in a similar manner to record and give out information regarding holidays which are called Z days. Processing of these inquiry orders is accomplished in Cycle I.

(10) Orders involving write-up of X and Z day information.The overall status of availability on each leg for X days, and also for Z days is frequently to be posted on appropriate channels of the drum in accordance with changes made in a correlative clerical inventory record. The magnetic recording of l for availability on all X days, or on all Z days expedites the answering of inquiries for these future dates. The magnetic recording of 0" for any leg indicates that on some one or more of the X days or Z days the seats have been sold out. The clerical record is then consulted for information regarding available space on days beyond the ten-day active period. The write-up of information on orders of this No. 10 type is handled from the master agents set and in the same manner as for writing up new inventory balances, the No. 6 types of orders.

DEFINITIONS In order to simplify the description, it may be well to give here a limited glossary of definitions and a brief explanation of certain functions performed by a few of the components.

Seeker.This is a rotary switch used to seize the common equipment if it is not busy, and to send back a busy signal (with the aid of certain relays) if it is busy. In case the common equipment is idle at the time a call is placed, the seeker responds by causing a gang relay at the calling station to connect that station through a multiple conductor cable with all the controllable compo nents of the common equipment and also to lock out all of the other keysets.

Decoder.Decoders are generally of the type known as relay pyramids. The code signal, as transmitted, usually relates to an individual item, so the relay pyramids designate one of a number of different outgoing circuits from a decoder as a selected circuit for any particular use.

Day plugb0ard.Tl1is unit is in the form of a plug board whereby input and output circuits may be interconnected by manipulatable jumper cords. Selective circuit controlled by conventional day-of-the-month keys on the keyset are carried through the plug board to ten assigned day selection relays plus two relays for X and Z days.

Transceivers-These are storage units for receiving messages from remote sets and for holding the intelligence until it can be used in an otherwise unoccupied time interval in connection with the common equipment. The master seeker gives access to the common equipment whenever it is freed from handling a previous order.

Electronic counters and counting rings.These are well known in the art and are used in several of the compo- Another channel is nents of the instant invention, including units 21, 24, 32 and 38. Each stage of the counter is a trigger circuit, sometimes called a flip-flop, or Eccles-Jordan circuit. Control, or stepping pulses are applied to the lowest order stage, and carry pulses are delivered by each stage to the next higher order stage so as to register the count progressively in binary numbers.

Gare.A circuit, well known in the art, having an output and a multiplicity of inputs so designed that the output is energized when and only when a certain definite set of input conditions are met.

L0ck. A lock is used in somewhat the same sense as a gate, but may have only one control circuit. It is usually in the form of an electron tube, but may otherwise be a magnetic relay, provided the timing tolerances will permit.

Delay multivibrator.--The operational requirements of our programming equipment are such that delays of 50 micro-seconds or more must be introduced into the timing of certain functions so as to follow one another in proper sequence. The delay multivibrator is a self-restoring flip-flop circuit which yields a dynamic pulse as its output at the end of its natural cycle.

C0n1para!Or.Where a code signal of one pattern is to be compared with a series of code signals having variable patterns, the comparator finds the instant of coincidence between the two patterns and delivers a gate pulse which lasts only as long as the two codes agree.

Encoding matrix.This unit receives a signal as delivered to it by any one of a plurality of different circuits. It translates the single-circuit pulse into a multi-element code pattern which identifies the source of the pulse.

Decoding matrix.This unit is controlled by simultaneously applied input potentials and yields a useful output potential only when there is agreement between the code pattern of said input potentials and the predetermined arrangement of the input circuit connections as chosen for detection of a particular code.

Shift regimen-Shift registers are used to store a train of code signals. The signals are injected successively at the input stage of the register and are passed along through the register from stage to stage, the transfer taking place only at the rate of succession of the input pulses. When a code pattern is thus stored in the shift register it remains there indefinitely and its significance may be sensed at any time and repeatedly, if desired. The pulses issuing from the last stage are not used in our system and are, therefore discarded.

PROGRAMMING The programming is of two main types. The simpler type is called Cycle I. It merely searches for information, as when availability requests are handled. The availability request always requires information with regard to eight different legs or individual flights. The address for a leg inventory is found in one revolution of the drum. In the next following revolution the inventory itself is found, and when read out it is injected into the computer. Signals representing the number of seats requested are also applied to the computer. Subtraction takes place automatically and the answer-back" signal is given out as CHK or REJ. Each of these answer-back signals is stored in an availability register and subsequently transmitted back to lamps on the agents set. Cycle I therefore involves two revolutions of the drum for each of the leg inquiries. A detailed response to the eight leg availability inquiry is indicated by the selective lighting of individual lamps on the agents set. These lamps are arranged in a row opposite designations on the coded plate which was disclosed in Schmidts application above cited. If space is available the lamp is lit. If it is not available, the lamp remains extinguished. The reduced balance of the inventory is not recorded because, for the execution of this order, no change in the balance should be made.

In handling a sale, the programming Cycle I must be completed the same as for handling an inquiry of availability. This cycle is required particularly to operate a storage register in which there is obtained in integration of availability tests with regard to all designated legs of a multiple leg trip. Even for a single leg flight the same procedure is followed for the sake of uniformity of programming.

If the integrated availability register does not give a reject signal, then the programming unit is permitted to carry on and to execute Cycle II. During this cycle the drum makes three revolutions for each designated leg that is involved in the sales order.

Cycle 11 includes the following operations which are performed in successive revolutions:

Revolution ].Inventory address read-out and storage in shift register.

Revolution 2.-Inventory item read-out and storage in the computer, where the number of seats requested is subtracted and a CHK (or Check) signal is sent to the answerback storage unit.

Revolution 3.-The new inventory balance is recorded in place of the old balance.

The performance of Cycle II, therefore, comprehends repeating the above 3-revolution operations successively for each of the designated legs. Hence, if the maximum number of eight legs were involved in selling a through ticket, then the total of drum revolutions required to execute this sale order is 40. Frequently, however, the sale of a seat reservation would involve only one to three or four legs, in which case the scanning requirements for read-out of the addresses and inventories and for writing in the new inventory balances would be restricted to five revolutions per designated leg.

The computer is so rapid in operation that it is prepared to deliver a new leg inventory balance immediately upon completing the second revolution (of Cycle II) in respect to the particular leg for which the computation is made.

Each of the orders enumerated in a previous chapter falls logically into one or the other of two categories, namely, those involving Cycle I only, and those in which it is necessary to perform Cycles I and II in succession. This last mentioned category is restricted to the following orders:

(2) Selling a seat reservation (3) Limited cancel orders (4) Unlimited cancel orders.

COORDINATION OF COMPONENTS Referring now to FIGS. 1 and 2, we show therein two typical agents sets 1, a control set 2, and a master set 3. Also there is a block representation of one or more transceivers 4, a line connector 5, and remote sets 6, which are capable of use in the same manner as the local agents sets 1, but through connection to the transceivers (storage units) over leased lines and through the line connector 5. The master seeker 7 and its function have been described above. Circuits common to all of the agents and control sets are connected individually to the common equipment in response to the operations of the seeker switch. These circuits are shown in the drawing to be contained in cable 8. They are distributed at the central station to the various components of the common equipment which are to be operated.

In the date-decoder 9, any one of twelve date sections of the storage equipment may be selected. The coordination between the calendar arrangement of keys in the key set and the date sections is changed from day to day, as the inventories become obsolete. Only eight wires are required to code any date but, since the inventory has to be changed with respect to obsolete information, and to substitute an entirely new inventory for a date ten days ahead, it is necessary to translate a date signal into a spe cific storage section of the inventory. The date-decoder 9 and the date-day plug board 10 are used for this purpose. The output of the unit 10 is constituted as a 12-wire cable till leading to individual gang relays which serve to select a 7-channel family of inventory digit records to be scanned only with respect to the desired date or group of dates beyond the ten-day period. In addition to the ten days in which inventory balances are maintained for each leg, there are two additional channels of recordings, one for X days and the other for Z days. These channels are used to give yes" and no answers to inquiries, but without maintaining arithmetical balances of the inventories. This simplified form of handling the X and Z day availability inquiries compares with the arithmetic method of inventory maintenance in that for X and Z days the inventory balance is either 1 or 0. When the answer is 1 it is apparent that the agent may immediately sell a reservation to his customer. If the answer is 0," it does not necessarily mean that there is no other space available, but definite information can be obtained through currently used clerical record keeping, as previously explained. Even in the case of these X and Z day reservations, considerable time is saved in answering inquiries. The common equipment operates the same for one day as for another. The day relay selector unit 11 merely switches the effects of the order execution into different ones of the twelve day-families of inventory channels on the magnetic drum 12.

The date selection having been made in the abovedescribed manner, the number of seats requested being set up on the keyset and the agent having set into his machine a coded plate for selection of a group of legs with which the customer is interested a switch key (not shown) on the agents set is thrown to a position for making an availability check. The agent then depresses a start key. The master seeker responds by establishing all necessary connections to the common equipment, provided the latter is not busy with another call. The code-notched selection plate, as used in the presently described embodiment, sends a nine unit-signal. Five of the code units of this signal serve to control a relay selector 14 of pyramidal form. This selector picks out one of 21 address channels to be scanned for addresses of the eight leg inventories designated by the plate. The five circuits involved are closed permutationally for operation of five individual relays in the relay pyramid. The possible permutations are thirty-two in number, but only twenty-one such permutations are used in the present embodiment. Each of these selections provides a connection between one of twentyone address reading heads 13, through contacts of the relay pyramid 14 to a read-out amplifier 15. The output from this amplifier is deliverable through an address sampling gate 16 to an inventory address shift register 17. The sampling gate 16 restricts this read-out operation to approximately ,6 of a drum revolution. Thus each address channel has a capacity for recording 96 addresses of leg inventories. A group of eight such addresses is selected by the use of a four-unit code section of the signal transmitted by the agents code-notched designation plate.

THE SYNCHRONIZING PULSE CHANNELS We employ five synchronizing pulse channels 19, each to give a different number of pulses per revolution. All of the reading heads which scan these channels are generators of these synchronizing pulses and the pulses themselves are amplified in separate amplifier circuits of the group 35. The output circuits from these amplifiers are labeled according to the number of pulses per revolution of the drum, thus: I/R; 16/R; 96/R; 960/R; 1024/R.

These output circuits are also labeled as conductors 1, 2, 3, 4 and 5, branching out from cable 20 to different portions of the system for synchronizing purposes according to the number of pulses that may be required in each revolution of the drum.

ADDRESS GROUP SELECTION FOR ONE- TNELFTH OF A REVOLUTION In order to make this group selection, a train of synchromzing pulses is required. This train comprises 16 pulses per revolution, as generated by one of the pulse channels 19, amplified by one of the amplifiers of the group 35, and taken through conductor 2 in cable 20 to a pulse counter 21. This counter, because it has four binary digit stages, has a repetitive counting cycle of 16 steps from binary 0001 to 1111 and is reset to 0000 on counting the 16th pulse. But We need only twelve counts for address group selection. Therefore we prefer to complete the cycle by generating four pulses rapidly during a socalled gap-time which separates the start of a read-out period covering one revolution of the drum from the end of such a read-out period covering a previous revolution. The sole purpose of the 13th to 16th synchronizing pulse counts during the gap time is to simplify the process of re-setting the counter 21 back to the binary registration 0000.

Conductor 2 in cable 20 delivers the 16 pulses per drum revolution, 12 of which are spaced apart suitably for dividing the record portion of each address channel into 12 equal sectors, each extending through an arc of slightly less than 30. In each of these sectors the address codes for eight different legs are recorded on drum 12.

Group selection relays of the unit 22 are locked up during the execution of any order. The code pattern thus stored is applied as a high or low voltage on each of four conductors leading to separate digital stages of an electronic comparator 18. These same stages are also fed from the output circuits of the four digital stages in the pulse counter 21. When the changing pattern of high and low output voltages from the counter matches that of the binary number stored in unit 22, the comparator attempts to operate lock 33 for releasing a sampling gate signal. But the duration of this effort is for one twelfth of a revolution of the drum. In that time eight addresses of the grouped leg inventories are scanned. So, in each drum revolution assigned to address scanning, it is necessary to select A; of of the address channel as the sector to supply a single address for one leg inventory. The comparator 23 performs this function, and in the following manner:

ADDRESS LEG SELECTION Each of the leg addresses in a given group is numbered 1, 2 8, and, when called for, is represented by a separate one of eight locked-up relays in the unit 31.

We prefer to carry out the process of individual leg address selection by read-out and storage of only one leg address at a time, and to replace each stored address by another during some part of every odd numbered drum revolution that occurs within the period required to execute an order.

The comparator 23 serves to find the location of a wanted address record by successively matching the output circuit voltage pattern of three counting chain digits, as delivered by the synchronizing pulse counter 24, against the static output from an encoding matrix 30 which repre sents the binary equivalent of an individual leg number Within a selected 8-leg group. This leg number is supplied by a special counting ring 32 which normally has an 8- pulse counting cycle, but which (as will later be explained) has facilities for making a skip'selection of leg addresses so as to avoid lengthening the search to as many as sixteen, or even more revolutions of the drum. For it will later be shown that if a sale order were to be executed and the trip happened to be one covering eight legs of a single flight, then an availability search (termed Cycle I) would require two revolutions of the drum per leg and would need to be followed by what we call a Cycle II operation, where three drum revolutions per leg are required in order to (1) read out each leg address, (2) read out each leg inventory, and (3) record a revised leg inventory balance. So, if fewer than eight legs are involved in such an order, its execution can be completed during a number of drum revolutions equal to only five times the number of legs involved. Cycles I and II are both included in this reckonmg.

We revert now to a consideration of how an AVAIL- ABILITY order is to be executed. This order requires only two drum revolutions per leg, but always the full quota of eight legs. All of the 8 relays in unit 31 must be operated and must cause the counting ring 32 to take eight steps, each step being made during the gap time at the start of an odd numbered drum revolution. The necessary timing controls are supplied by the programming unit 34, as will be explained in due course. It is sufficient to state here that a reset pulse is delivered to the counting ring 32 via conductor 631 which is one of the output circuits from the program unit 34. Following the reset pulse is a start pulse delivered to the counting ring over conductor 630. Next there are stepping pulses which are delivered during gap time over conductor 623 at the start of each odd numbered revolution following the first.

When all of the relays of unit 31 are operated at the same time the counting ring 32 is thereby directed to step forward through its complete cycle and to deliver negative static pulses progressively through each of the eight conductors 25 to the encoding matrix 30. The steps of this cycle are taken at the start of each odd numbered revolution, under control of dynamic gating pulses delivered through conductor 623, but commencing at the start of the third revolution.

The circuit connections of the matrix 30 are such that it is caused to encode the representation of binary numbers successively in response to the progressive application of negative voltages to each of the conductors 25. This encoding function results in the delivery of the binary number patterns on output circuits 29 leading to the comparator 33. The pattern changes at the start of the odd numbered revolutions, the first leg designation being the binary number 001; the 7th is 111, and the 8th designation is binary number 000.

The comparator 23 functions to establish coincidence between the pattern of the three element code delivered by the encoding matrix 30 and the pattern of binary numbers 001 through 111 to 000, as composed by a synchronizing pulse counter 24.

Counter 24 operates continuously during the execution of any order. It responds to amplified read-out pulses as generated and carried through conductor 3 branching out of cable 20. There are 96 such pulses which are delivered during each revolution of the drum.

The counter 24 has a repeating cycle of eight steps and because there are 96 synchronizing pulses per revolution, the counter repeats its cycle twelve times per revolution. The binary representation of counts 001 through 111 to 000 inclusive is thus presented to the comparator 23 twelve times per revolution of the drum. Now, remembering that the binary number pattern as delivered to the comparator 23 over conductors 29 is changed only at the start of each odd numbered revolution, it will be seen that coincidence between the simultaneously presented code patterns will occur once in each twelfth of a revolution. The particular twelfth which is significant has been established, as heretofore explained, by the functioning of the comparator 18. So, with the progression of the S-leg ring 32 through its cycle, the scanning of different leg addresses is made available in successive odd revolutions of the drum, but restricted to that twelfth of a revolution which was selected by the group selection relays 22. There is, therefore, a cooperative action in which the two comparators 18 and 23 participate for the purpose of releasing a joint control lock 33 just long enough during each odd revolution to read out one leg inventory address, and to read out a diiferent one of eight such addresses in successive odd revolutions.

The joint control lock 33 shown in FIG. 2 is an electronic circuit arrangement which is intimately associated with the two comparator units 18 and 23 and is controlled by them. It is also subject to control by pulses coming from a matrix 615 in the program unit 34. These pulses are applied to the lock 33 over conductor 646 and cause the lock to be released only during odd revolutions 11 of the drum. The output pulse from lock 33 persists just long enough for one leg address consisting of ten code pulses to be read out by the sampling gate 16 under control of signals from one of the reading heads 13 as fed through the amplifier 15.

THE INVENTORY ADDRESS SHIFT REGISTER The shift register 17 was briefly described in the chapter entitled Definitions. It is composed of ten stage electronic device into which pulses are fed successively as read out from an address channel and passed along by the address sampling gate 16. In the sampling gate the polarities of the pulses are differentiated by means of synchronizing gate pulses which are delivered at the rate of 960 per revolution, these being applied through condoctor 4 of the sync. pulse channels, a read amplifier 35 and a sync. pulse gate 36. The train of ten pulses which are permitted by the joint control lock 33 to be passed along by the address sampling gate 16 become stored in the shift register 17 during odd numbered revolutions of Cycle 1, or revolutions A of Cycle II (as will be explained later in reference to the execution of other types of orders). The code signal for each leg address remains stored in the shift register 17 throughout a subsequent revolution of the drum (Rev. B) and is then replaced by another one of the eight leg addresses until all of them have been used to locate corresponding leg inventories. The replacements are according to the timing action of the lock 33, as previously explained; each individual read-out of a leg address being from a different sector of an address channel within a selected f the channel circumference.

THE READ-OUT OF LEG INVENTORIES This read-out operation is performed during even numbered revolutions of Cycle I, the execution of Availability orders still being under discussion. Matrix 616 in the program unit 34 delivers an enabling voltage on conductor 648 to a lock 28 for releasing a comparator 39 so that the latter will respond to the joint control of signals from an INVENTORY SYNC. COUNT register 38 during even numbered revolutions of the drum. This counter is advanced by sync. pulses delivered through conductor of cable 20. The counter 38 is electronic and has a repeating cycle such that it will register binary numbers from 0000001 through 1111111 and at the l024th step it will be reset to 0000000. This cycle is completed once during every revolution, but is effective only during Rev. B, as governed by the enabling voltage on conductor 648.

Like other comparators heretofore discussed, the comparator 39 functions to determine the moment of coincidence between two binary numbers. Here the code representing a leg address as stored in the shift register 17 is met by the progressively obtained binary numbers issuing from the sync. pulse counter 38. When the two numbers are matched the comparator 39 delivers a gating signal to a device 40 which is labeled 7 GATED REGIS- TERS. This device comprises individual flip-flop circuit elements for the seven digital stages of a binary number to be read out from the leg inventory channels. The actual read-out operation goes on continuously as a function of the READ & WRITE HEADS 26, scanning the leg inventory channels. Only the 7-channel family which is selected by one of the day relays 11 is effective to deliver the read-out pulses to an amplifier and discriminator unit 41 consisting of a separate amplifier and discriminator for each channel, or digit of the binary number representing an inventory balance.

The seven gated registers 40 operate simultaneously in response to gating control by the comparator 39 whenever coincidence is established between the number stored in the shift register 17 and the sync. pulse counter 38. At the instant of finding this coincidence the binary number representing the inventory balance of the desired leg is transferred to and held in the registers 40. The seven 12 digits of this binary number are immediately presented to the computer 42 as a minuend from which a quantity representing the number of seats wanted by a prospective customer is now subtracted. The seats-wanted-number was stored in the computer 42 from the outset of executing an Availability request order.

THE COMPUTER This computer component 42 comprises electronic equipment including individual flip-flop circuits for each of seven digital orders of the number representing an inventory balance, or a result of potentially changing that balance by the amount of an introduced subtrahend or addend coming from one of the keysets. When executing an Availability order, the computer delivers its results only in terms of a Check signal or a Reject signal with respect to each of the eight leg inventories of a selected group. The results are transferred through conductor 54 to an electronic storage unit 43 which is labeled DISTRIBUTIVE ELECTRONIC STORAGE. This unit has eight separate storage elements which are successively made receptive to the signals applied through conductor 54. The distribution is under control of gating pulses delivered by the leg ring 32. With each setting of the leg ring a static voltage goes out on one of eight conductors 27 for selecting a different one of the storage elements in unit 43 to receive the CHK or REJ" signal and to store the same until released as an answerback signal train. An availability answer relay group 44 is actuated under control of the storage elements 43, and serves to transmit the answers over eight wires in cable 8 back to indicator lamps in the agents set.

THE PROGRAMMING EQUIPMENT 34 While the block 34 has been shown in FIG. 1 to represent certain programming functions, the mode of operation of this equipment will be more clearly explained by reference to FIG. 6 which shows in block diagram form the principal components of the programming equipment.

One of the synchronizing pulse circuits includes conductor 1 in cable 20 and supplies one pulse per revolution (called a gap reset pulse) prior to each drum revolution scanning cycle. The first effective gap reset pulse is that which when delayed by microseconds follows a positive start signal originated at one of the calling stations-an agents set, for example. This start signal comes in on conductor 606 and is delivered to a so-called set-reset flip-flop 607. When the equipment is idle, the flip-flop circuit 607 stands set to a stable state from which it cannot be shifted by repeated delayed gap reset pulses. At the outset of receiving a call the positive start signal triggers the flip-flop 607 to the other stable state so that the following delayed gap reset pulse will restore unit 607 to its original stable state and in doing so will cause it to deliver a positive differential pulse to another set-reset flip-flop circuit 608. Unit 608 is one which is set to an Off stable state by a dynamic positive pulse, called a stop signal. Unit 608 is thereafter responsive to a positive differentiated pulse from unit 607 at an instant when a delayed gap reset pulse is applied to unit 607 for causing its differentiated output pulse to be positive. Unit 608 then stands at that setting for as many drum revolutions as are required to execute an order.

There are three multivibrator delay circuits 601, 602 and 603, each of which produces a delay of substantially 50 microseconds. These delay circuits intervene between the pulse input to the unit 601 and the output from unit 603. Each has a differentiated positive output pulse at the end of the delay period, as shown by the labeling of the respective output circuits as D," for dynamic and in contradistinction to other circuits labeled S for static. The overall delay produced by units 601, 602 and 603 amounts to 150 microseconds and is intended to allow for various resetting and timing operations to be performed during the gap period of drum revolutions.

13 The 150 microsecond delay applied to the sync. pulse control as given to the unit 607 from the output of unit 603.

There are five units of the programming device the operation of which is subject to direct conditioning control from the unit 608, namelygates 604, 605, 622, mixer circuit 626 and a set-reset flip-flop" 628. These are served respectively by control circuits as follows:

Gate 604.-Gate 604 is one which receives a delayed dynamic synchronizing pulse once per revolution as output from the delay multivibrator unit 601. This gate 604, however, will not respond to sync. pulses until it is conditioned to do so by the static output from unit 608. Thereafter the gate 604 repeatedly delivers dynamic pulses once per revolution and with a delay of fifty microseconds during the on time of the programming equipment.

Gare 605.Gate 605 is one which must be caused to deliver a dynamic output pulse once per revolution but delayed by 100 microseconds and repeated for as many times as required to fill an order. The conditioning of the gate 605 is effected by the positive output voltage from unit 608 Which persists during the operate time of the programming device. At the start of the operate time, however, the drum makes one substantially full revolution before the first dynamic pulse out of unit 602 is transmitted through gate 605. This is due to the delay difference of 50 microseconds that separates the output pulses from unit 608 and 602 respectively.

Gate 622.One branch 649 of the output circuit from unit 608 carries a static pulse to an input terminal on gate 622. This gate is thus conditioned at the start of an order execution to respond to a dynamic pulse which is delivered to another of its input terminals and comes from a mixer circuit 621. The mixer circuit is variably controlled, depending on whether Cycle 1 or Cycle II is to be processed, as will be explained in due course. The output circuit 623 carries a start pulse from gate 622 to the electronic counting ring 32 which has previously been described and which is used to select different leg addresses to be scanned and stored.

Mixer circuit 626.-This mixer circuit 626 is variably controlled, but at the start of an order it receives a dynamic pulse from unit 608 which is passed along as a reset pulse over conductor 631 to the leg ring 32. This mixer circuit also delivers its dynamic output pulse to a delay multivibrator 629, the output from which is utilized in several ways, as will be explained presently.

Flip-flop circuit 628.-This flip-flop circuit 628 is triggered to one side by the positive dynamic pulse applied through conductor 649 at the start of the Cycle I operation. It holds that stable state until Cycle I is completed since repetitive pulses at the start of successive revolutions have no effect. When relay 627 is operated, however, for the purpose of starting a Cycle II operation under further control of a delayed output pulse from unit 625, this delayed pulse re-sets the flip-flop to the other stable state in opposition to the setting produced by the pulse applied through conductor 649.

Revolution counters 610 and 6]1.A fundamental function of the programming unit is to distinguish between first, second and third revolutions of the drum because of different operations which are to be performed during these revolutions. Therefore, we have a counter 610 which is also labeled 2' because it gives a binary count in the first order of digits and is shifted back and forth as a flip-flop circuit every revolution to distinguish between odd and even revolution. This counter when re-set register "0 and after the first drum revolution of an order execution its stable condition is shifted to a 1 registration by a pulse from gate 665 through mixer 609.

Counter 611 is held eifectively idle during Cycle I by means including the Either Gate 620, presently to be described. During Cycle II counter 611 responds Leg l I 2 3etc.

Counter 610 010 010 010 Counter (ill 001 001 001 Operatively associated with the counters 610 and 611 are inverter tubes 612 and 613, the functions of which are to reverse the polarities of the voltages delivered from counters 610 and 611 respectively.

The counters 610 and 611 and the inverters 612 and 613 are employed to set different matrices 615, 616, 617 and 618 so that each of these matrices will be enabled to deliver static outputs during operate time of the programming device where the several outputs are timed (as during Cycle 11 operation) to cover three different drum revolutions for scanning purposes and to utilize the approach to a fourth revolution for resetting the counters, 610 and 611. Positive output potentials from these matrices are permitted only during the operate time of the programming unit and under control of the negative static output from an inverter tube 614, the input potential for which is derived from the unit 608.

The revolution counting matrl'ccs.-Matrix 615 identifies the first drum revolution for each leg selection. It operates under the control of the two inverters 612 and 613, each of which has a negative output control voltage to be applied to the matrix. Matrix 616 is representative of the second revolution of the drum and is jointly controlled by the output from counter 610 and from the inverter 613. Both of these outputs must be negative during the second revolution.

Matrices 617 and 618 have no useful function during Cycle I and, in fact, they deliver no positive output pulses except when Cycle 11 is processed. Matrix 617 is jointly controlled by counter 611 and inverter 612, the outputs from these two units being negative during the third revolution. At the approach to the fourth revolution, matrix 618 is set to deliver a positive pulse, being jointly controlled by the output from the two counters 610 and 611. This matrix 618 performs its function of resetting the counters at the approximate start of the fourth revolution by controlling a delay multlvibrator unit 619, the output from which is fed to the mixer circuit 609 and thence to one of the input circuits of counter 610, giving the latter an extra counting pulse so that it and counter 611 will both be reset to 0.

As has been explained in the foregoing part of the description, certain orders, like an availability check, can be carried out within the period of only two revolutions of. the drum. In such cases, resetting of the counters is a matter of normal cycling and occurs at the end of every second revolution.

Output circuits from the matrices-Matrix 615 delivers a positive potential during the odd revolutions of Cycle I, and during the first of every three revolutions of Cycle II. The differences of revolution counting as between Cycle I and Cycle II will presently be explained. They are under control of the components 628 and 620. What we are now considering, however, is the utilization of output from the several matrices under varying conditions as determined by the dihIerent orders to be executed.

The output circuit 646 from matrix 615 leads to the joint control lock 33 and serves to isolate the address sampling gate 16 from comparators l8 and 23 during even numbered revolutions (considering Cycle I operation), when the matrix output is negative; and to release the sampling pulse to the address sampling gate 16 during odd numbered revolutions, the matrix output being positive.

Matrix 615 also conditions a gate 642 to respond to dynamic pulses from gate 604 at the end of each odd numbered revolution during Cycle I and the first, fourth, seventh, etc. revolutions of Cycle II. Gate 642 has an output circuit 645 leading to an address sampling storage unit 50. When the master agent wishes to check the correctness of any leg address, his set 3 can be manipulated so as to instruct the address sampling storage unit 50 to send back via answer-back signals a copy of the read-out from any selected leg address. The storage unit 50 continually copies the read-out of addresses as given to the address shift register 17. The pulse from gate 642 and the instruction signal from the keyset 3 are jointly effective in selecting and timing the transmission of the answer-back signal for inventory address sampling, but the timing has to be at the end of an odd numbered revolution.

The output circuit 648 from matrix 616 leads to a lock 28, the function of which has been described in connection with the comparator 39 for the readout of selected inventory balances during even numbered revolutions of Cycle I, or during revolutions B of Cycle II. Matrix 616 gives out a static positive voltage during these revolutions for enabling the comparator 39 to function.

Matrix 616 also conditions gate 643 to respond to dynamic pulses from gate 604 at the end of each even numbered revolution during Cycle I. Gate 643 has an output circuit 647 leading to an inventory sampling storage unit 51. When the master agent wishes to check the current reading of any leg inventory, his set 3 can be manipulated so as to instruct the inventory sampling storage unit 51 to send back via answer-back signals a copy of the read-out of any selected leg inventory. The readout signals have their storage in the 7 gated registers and are injected into the computer 42 in accordance with a previously described procedure. When the master agent merely wants to make a check of inventory balances his keyset can be manipulated the same as for making an availability inquiry, except that the number of seats wanted would be zero. When subtracted from the inventory its current reading can be transferred from the computer to the inventory sampling storage unit 51 and gated out as an answer-back signals to the master agents set .3 in which lamps are provided for setting up an indication of the binary number representing the inventory balance. The answer-back signal is transmitted at the end of an even numbered revolution of Cycle I as determined by the timing pulse from gate 604 delivered through the gate 643 to its output circuit 647, as above described.

Matrix 617 is intended to deliver a positive static potential during a third revolution of the drum, and will do so if the counting cycle is allowed to proceed beyond the second revolution. In processing Cycle I a third revolution is never reached because only two revolutions per leg are necessary. The Cycle II process involves recording new inventory balances, as derived from the computer 42 after taking the time of the second revolution to read out the old balance. Hence, the output circuit 650 from matrix 617 serves to release a lock 46, thereby to feed the output from seven gated amplifiers 45 through the multiple unit 41 and through contacts of the selected day relay 11 to the proper read-and-write-heads 26. The signals for this recording operation come from the computer 42. However, it is only when recording new inventories that result from sales and cancellation orders that Cycle 11 processing is necessary.

When a starting inventory balance is to be written this can be done during the second revolution upon signaling instructions from the master agents set 3. In this case it is apparent that such instructions would, by suitable operation of a relay (not shown), disable the read-out registers 40 and would substitute the release of lock 46 during the second revolution. The binary code representing a starting inventory quantity (the seat capacity of a given plane) will then be transmitted to the computer 42 over seven wires in cable 57. The component 40 having 15 been reset to register zero, will, in this case, enable the computer to register the start inventory as added to zero, so it will be written in by the record amplifiers without alteration.

Matrix 618, representing a fourth revolution, or revolution D has a fleeting function which, when it is performed at the end of the third revolution, results in the immediate resetting of counters 6'10 and 611 to zero. Matrix 618 is, therefore, suicidal. The operation is called for only during the processing of Cycle II and will be explained in more detail in a later chapter devoted to the Cycle II process.

Programming for orders which require Cycle I only. For the purpose of filling an availability request order, also for filling several other types of orders, we require the programming device to operate so as to obtain a stop pulse at the end of the second revolution of the last designated leg selection. This means at the end of the 16th revolution in case of an availability order, where eight leg inventories are always interrogated. The leg addresses are searched during odd revolutions; that is, while matrix 6115 delivers its positive static output. The inventories are found and read out during even numbered revolutions; that is, while matrix 616 delivers its positive static output. The stop signal which is to terminate the functioning of the programming device is in this case derived from a mixer circuit 637, under control of a dynamic pulse which is delivered as output from a delay multivibrator 625. This unit 625 receives its control from gate 624 where the latter responds to a signal delivered by the leg ring 32 after it has reached the last step of leg selection. The gate 624 is jointly controlled by this pulse on lead 632 and by the output from the either gate unit 620. This joint control takes place only at the end of an evennumbered revolution provided the leg ring has reached its last step. The output from gate 624 is delivered to delay multivibrator 625, thence through contact a of unoperated relay 627 and to the mixer 637. The output from mixer 637 is delivered as a stop signal for restoring the flip-flop circuit 668 to its program terminating condition. Thus, Cycle I is ended and the call is terminated.

Progrmmning for Cycle Il.-ln a previous part of the specification ten different types of orders were enumerated, three of which require the operation of the system under both Cycle I and Cycle ll programming. For each of these three types of orders it will now be explained how the programming equipment operates. It should be borne in mind that Cycle II operation must always be preceded by Cycle I operation, even though there may seem to be a repetition of some of the functions of these two cycles. The reason for this is it must be determined in advance of executing a sale order or a cancellation order that there is no reason for rejection of such an order. If, for example, the customer calls for transportation on a trip which has more than one leg and if a search of availability shows that some one or more of the leg inventories is exhausted, then before the programming is carried any further a reject signal will be derived automatically from the operation of the computer. This will thereupon terminate the cycling and will cause the transmission of a reject signal to the agents set.

For the execution of any order which involves programming under both Cycle I and Cycle II, the relay 627 is operated under control of a signal from the agents set. This relay has several functions some of which need not be discussed at this point, although one may note that the relay winding is shown in two places for convenience of locating the two contacts a and b where they may best fit the circuit arrangement.

If Cycle I only is called for, it was explained in the foregoing description that a stop signal would be passed through the mixer 637 to the set-reset flip-flop unit 608 for causing it to render gate 605 insensitive to further gap reset pulses after the leg ring has completed its leg selecting cycle.

When, however, the execution of an order requires Cycle II to follow Cycle I, then relay 627 is operated and its transfer contact a carries a dynamic output pulse from the unit 625 to the reset flip-flop 628 after the leg ring has completed its leg selecting cycle under Cycle I operation. The stop-signal circuit is also opened, so that Cycle II may be performed.

Assuming that a customer calls for two seats on a 3-leg flight then the agent selects the proper three leg keys of his keyset. He depresses a 2 key in a strip for designating the number of seats wanted. The date keys are also properly depressed and a code plate is selected and inserted in the receptacle of the keyset for use in making the flight and leg selections, as explained in the Schmidt application aforementioned.

The keyset having been thus prepared to give a sell order, the agent throws a lever key to a position marked SELL. If the common equipment is not at the moment engaged in filling another order from a different keyset, then the order under discussion will be executed in the following manner and varied only according to whether the inventory will permit the number of seats wanted to be sold, or Whether the sale must be rejected due to a soldout condition:

Since the customer wants transportation on a flight that makes only two stops between his departure point and his destination, the sale of a reservation will involve searching three designated leg inventories for availability. Cycle I programming is for this purpose, and, when a sell order is given, the search can be limited to the scanning of only the leg addresses and leg inventories involved. Under the conditions now assumed Cycle I will be carried through to completion in only six revolutions of the drum, two for each leg, provided that each leg inventory shows space to be available. The leg ring will then send its completion signal through conductor 632 to gate 624. Gate 624 is then prepared for opening by an output pulse from the so-called either gate 620 at the end of the next even numbered drum revolution. When gate 624 is opened at the end of Cycle 1, relay 627 having been operated for a Sell order, a pulse is delivered through the delay multivibrator 625, transfer contact a of relay 627 and thence to the set-reset flip-flop 628, as before stated. If, however, the order cannot be filled because of insufiicient space available, the stop signal will come in on conductor 56 and through contact of relay 627 to gate 640, thence to mixer 637 and flip-flop 608 and will terminate the processing of the order before Cycle II is started.

The flip-flop unit 628 having been triggered causes a new control to be exercised whereby the either gate 620 will deliver its output pulses during the Cycle II process only at the end of every third revolution of the drum. How this is done will best be explained by refer ence to FIG. 4 which shows the details of the either gate" 620 that appears in FIG. 6 only as a black box.

The either gate with lock 620-This gate derives its name from the fact that it functions in either of two ways. During Cycle I it is required to deliver a stepping pulse to the leg ring after every even numbered revolution. During Cycle II the same stepping pulse must be delivered only after every third revolution of the drum.

Gate 620 comprises two pentode tubes 401 and 402 and three triodes 403, 404 and 405, two of which may be enclosed in the same envelope if desired. An unused triode is shown to be enveloped with triode 405 merely because in the design of the equipment twin triode tubes have been adopted as a standard.

There are three input terminals a, c and e which are correspondingly indicated in FIGS. 4 and 6. The output terminal d also appears in both figures. The usual operating potentials, 120 volts, 120 volts and a neutral ground are also indicated together with capacitors, resistors and voltage dividers, all according to conventions which need no explanation.

This either gate, during the processing of Cycle I is controlled by positive dynamic pulses derived from counter 610 at the start of the odd numbered revolutions. The pulses are applied at input terminal c of the gate. At the input terminal 6 a static negative voltage is applied from the flip-flop circuit 628 throughout Cycle I operation. This maintains a non-conductive state in pentode 401 so that the screen grid voltage therein is high, causing the first grid of pentode 402 and the control grid of triode 403 both to produce conduction. The cathode of triode 403 is then driven positive and operates to lock out the application of positive pulses through capacitor 406 to the third grid of pentode 401. Pentode 402, because of its conductive state at least as far as the screen grid, is subject to control by positive dynamic input signals applied to its third grid. When so applied the anode potential drops sufficiently to impress a blocking potential on the normally conductive triode 404. This is an inverter wherein variations of anode potential are used to control a cathode follower 405 which is normally blocked. 80, under dynamic pulse control, as applied to terminal c, the either gate 620 functions to deliver output pulses from terminal d during Cycle I at the end of every even numbered revolution. These output pulses are utilized by the mixer 621 and the gate 622 to deliver stepping pulses over conductor 623 to the leg ring 32, as has previously been explained. Gate 624 also utilizes the output from gate 620 at the end of Cycle I, as indicated by the delivery of the signal over conductor 632 from the leg ring, and as previously explained.

Another function performed by the negative voltage output from flip-flop circuit 628 during Cycle I and applied to terminal 2 of the gate-lock 620 is explained as follows: This negative, voltage blocking pentode 401 and driving triode 403 conductive, holds terminal a of gate 620 positive. as previously explained. Furthermore, the positive voltage is fed back from terminal a through the output circuit of counter 611 to the input terminal of the inverter 613 and to the input sides of matrices 617 and 618. These three units are, therefore, held inoperative during Cycle I. This is desirable for their functions are performed only in connection with the processing of Cycle II. However, the output of the inverter 613 during Cycle I is held negative as applied to terminals b of matrices 615 and 616, the same as though inverter 613 received its control solely from counter 611. The normal representation of odd revolutions by matrix 615 and even revolutions by matrix 616 is therefore, not disturbed by the fact that inverter 613 is inoperative.

The triggering of the flip-flop circuit 628 at the end of Cycle I (as previously explained) when Cycle II is to follow, enables the either gate 620 to operate so as to deliver a dynamic output pulse only at the end of every third revolution. The voltage now steadily applied to terminal e, and for the duration of Cycle II, is positive. This renders pentode 401 conductive at least as far as to its screen grid, dropping the potential of the screen grid so as to block the pentode 402 and the triode 403. Pentode 401 is thus enabled to respond to pulses applied at terminal a from counter 611. Matrix 617 at the start of the third revolution is set to deliver a Voltage through conductor 650 for releasing the lock 46 whereby new inventories are caused to be recorded during the third revolution of Cycle II.

It is important to observe at this point that the output from counter 611 has four elIects-(l) the dynamic pulse effect on pentode 401 which is positive at the attempted start of a fourth revolution (substantially the end of the third revolution) and causes the either gate to have its inverter 404 blocked and its cathode follower 405 made conductive, thus delivering the dynamic pulse to terminal d after third revolutions of Cycle II instead of after second revolutions of Cycle I, but for the same functional requirements. The reference to a fourth revolution as having an attempted start means that there is no true fourth revolution because as soon as its start is indicated 19 by the output from matrix 618 (revolution D) that output itself after going through the multivibrator 619 and mixer 609 supplies an extra counting pulse to the counter 610, and restores the two counters 610 and 611 to their initial setting at which they both deliver output potentials for a new first revolution.

Elfect (2) of the changing output from counter 611 is static. This output is during the first two revolutions and causes inverter 613 to apply negative controls to input terminals b of matrices 615 and 616 so that the latter will alternately deliver output pulses in response to control by counter 610. Effect (3) is to deliver a static negative voltage to one of the input circuits of matrix 617 throughout the third revolution so that its output may be utilized as explained in an earlier part of this specification. Effect (4) is also static. Jointly with negative voltage from counter 610 at the attempted start of the fourth revolution matrix 618 is caused to deliver the output pulse which re-sets the counters 610 and 611 substantially at the end of the third revolution.

Termination of the Cycle II pr0cess.After the leg ring 32 has been stepped to the last designated leg position and rested there for three revolutions of the drum, we have a condition at which Cycle II must be ended. Three factors are coincident at this time: (1) Relay 627 remains operated so that the stop signal cannot go through to mixer 637 as was provided for terminating Cycle I. (2) The leg ring has delivered its Last designated leg signal through conductor 632 to gate 624, and (3) gate 636 has been conditioned to operate by the positive potential output from flip-flop 628. Therefore when the either gate 620 delivers the next output pulse as an indication of the end of the third revolution for the last designated leg, that pulse is directed by gate 624 through unit 625 and through gate 636 to the mixer 637 from which it goes to the set-reset flip-flop 608 for resetting the same. This terminates the Cycle II process.

INVENTORY ADDRESS SELECTOR It has been indicated in the foregoing description that when selling orders and cancellation orders are to be executed, the particular legs involved in such transactions may be individually selected so as to determine the scanning times for individual leg addresses as serially disposed around the circumference of the address channels. Accordingly, the leg address selector 32 and, in cooperation therewith, the encoding matrix 30 and the comparator 23 are arranged to make skip selections, thereby to reduce the number of drum revolutions necessary to obtain all the wanted leg addresses for satisfying any given order. The inventory address selector has eight individual output circuits 23 which cyclically control the composition of different 3-element codes by the encoding matrix 30. Thus the sampling gate 16 is caused to open only when designated leg addresses are to be read out to the inventory address shift register 17.

FIG. 5 shows two stages of the eight-leg ring 32 with associated relays 31, whereby the designated legs are selected. Only the first and last stages of the ring are shown, since it will be understood that the intervening stages have similar circuit arrangements. In each stage two thin triode tubes and two pentode tubes are used. In the first stage the individual triodes are VlB and V3B, which are included in a flip-flop circuit, also a reset device V-3A and a cathode follower VlA. The tube complement of the first stage further includes two pentode tubes V2 and V4 called digit setters.

Tubes V2 and V4 are alternately conductive if the first stage is selected by relay 31 and when responding to stepping pulses. The first stepping pulse comes in on conductor 623 at the end of the second drum revolution after a start pulse is received on circuit 630. The second stepping pulse activates tube V4 and resets this stage to normal.

At the start of the first revolution a reset pulse is received on circuit 631 and is applied through capacitors 501 to triodes V3A and the like in each stage. This pulse serves (by making triode V3A conductive) to reset the flip-flop tubes, thus giving the entire leg ring 32 a clean slate. Triode VlB is then blocked and V3B is made conductive. Cathode follower VlA output is lowabout20 to -30 volts.

If leg address #1 is to be selected, relay 31 must be operated from the keyset in order to actuate stage #1 of the address selector ring. Then the start pulse coming in on circuit 630 drives the first grid in tube V2 positive. The screen grid of this tube will then have a lowered potential and will cause tube V4 to be completely blocked. Tube V2, however, will stand conditioned to respond to the first stepping pulse received on circuit 623. No other tube of the V-2 series in other stages will be so conditioned.

The stepping pulse is applied to the 3rd grids of all pentodes, all stages, but has no effect except in the one tube V-2 which has been selected, and in the V4 tubes of the remaining stages. The anode of tube V2 with reduced potential blocks triode V3B in the flip-flop circuit of the first stage. This action drives triode VlB conductive.

The cathode follower VlA is also controlled by the non-conductive state in triode V3B and is driven conductive. Its cathode is connected to one of the output circuits 25 leading to the encoding matrix 30 and to the storage unit 43. The matrix unit serves to make the leg address selection and the storage unit 42 serves to allocate the output signal from the computer (which has CHK or REI significance) to its proper storage element leading to the answer-back relays 44, the latter being individual to each leg of a selected leg group.

The pulse output from the cathode follower VlA is also utilized to condition tubes V-2 and V4 in the next succeeding designated stage. The conditioning circuit may be traced through contact b of the currently selected stage relay 31 to contact a of next succeeding selected stage. Any intervening stage relays 31 that have not been designated by keyset control will have their contacts a opened, but will pass the conditioning pulse through contact b, then closed against its back contact. Thus, only the designated stages of the ring will be actuated in succession.

Each time that a stepping pulse is received on circuit 623 it will cause triggering of the flip-flop circuit in the next designated stage, and will also cause a re-setting of the flip-flop circuit just previously triggered. Pentode tube V4 is used for this purpose. The start pulse on circuit 630 persists only until the end of the first revolution. Immediately thereafter, tube V2 becomes completely blocked and its screen grid potential resumes its normally high potential. This drives the first grid in tube V4 conductive and enables this tube to respond to the next stepping pulse. The function of tube V4 at this time is to block tube VlB as a re-setting operation for the flip-flop circuit. So each stage is restored to normal after delivering its pulse for two drum revolutions to its individual output conductor 25.

When the last stage of the address selector is reached, relay 31,, having been energized, not only is the digit 1 signalled from the cathode follower VlC through conductor 25 to the encoding matrix 30, but at the same time positive output potential is delivered through from contact and associated contact b of relay 31 to the stop signal circuit 632 for purposes heretofore described in connection with the programming unit 34.

Now, let it be assumed that a sale or a cancellation order is to be executed involving only legs 1 and 8 of the ring while legs 2 to 7 inclusive are to be skipped. In this case, failure to operate relays 31 to 31, inclusive leaves the stages for legs 2 to 7 undisturbed by the stepping pulses. In place of the transfer of the selecting pulse from cathode follower V1A through from contact and associated movable contact b of relay 31 to the second stage after the first stepping pulse has been applied, the cathode follower pulse from V-2A goes directly through contact a of the first, and in this case, the last stage to be reached. Here it is assumed that relays 31 and 31 are the only ones operated. In the illustrated example, this is the last stage of relay 318. Therefore pentode tube V-2A in the last stage is the one which responds to the second stepping pulse.

From the above it Will be seen that any desired pattern of leg designations may be defined by the successive steps of the leg ring according to the selection of stages as made by their respective relays 31. Each non-operated relay 31 causes its associated stage to be skipped in the leg ring stepping process. This considerably shortens the time necessary to execute sales and cancellation orders.

THE MATRICES-DECODING AND ENCODING FIG. 3 shows details of a typical decoding matrix such as is used in blocks 615, 616, 617, and 618 in FIG. 6. With slight modifications and circuit changes it becomes an encoding matrix such as is included in the component 30 and serves to translate individual circuit selections into different code patterns.

Assuming that the circuit arrangement of FIG. 3 is required to deliver a output potential whenever all three of its input terminals simultaneously receive negative pulses, these pulses will then render the three triodes 301, 302 and 303 non-conductive. Their anodes are interconnected and are coupled to the input circuit of triode 304, this being a cathode follower tube. Triode 305 has its cathode connected to the cathode of triode 304 and is arranged by its well-known circuit connections to place a negative limit, say volts minus with respect to ground, on the output signal terminal. Triode 306 has its grid connected to its anode and is, therefore, functionally a diode. Its cathode is grounded and its anode is coupled to the input circuit of triode 304. Triode 306 serves to prevent excessive -1 potential being applied to the grid of the cathode follower. Each of the input terminals is resistively connected to a bus 307 on which a potential of, say, 30 volts is maintained by means of a voltage divider connected between a -120 volts source terminal and ground.

The matrix as described in the preceding paragraph is used by us for timing the delivery of pulses in successive revolutions of the drum, as explained in the foregoing description of the Program unit 34. Each matrix of the group 615-618 has thre input terminals, two of which derive their controls either from the two counters 610 and 611, the two inverters 612 and 613, or one counter and one inverter; the pattern of connections being different for each matrix. The third input terminal of each matrix receives a constant negative potential from the inverter 614 during the entire period of execution of an order. So the output of pulses from each matrix is limited to times when all three of its input terminals are negative. Because of the different patterns of input circuit connections each matrix functions at a different time, and for the purposes hereinbefore described.

Considering now the encoding matrix 30 (FIG. 1), this component includes three basic matrix tube assemblies, each assembly comprising four cathode follower triodes, the cathodes of which are interconnected by a conductor which yields a output potential whenever any one of the cathode follower triode grids is driven Each cathode follower has its control grid connected to a particular on: of the conductors 25 coming from the leg ring unit 32. It will be recalled that pulses are transmitted singly and in succession at times governed by the stepping of the ring. The encoding matrix 30 is arranged to establish a different 3-element code in response to each of the pulses as delivered through a different conductor 25.

The encoding operation may be readily understood by Digit out from Cathode Follower Assemblies Position 01' Leg Ring 0 0 l) 0 0 l 0 l 0 0 1 l l 0 0 l 0 l l l 0 l 1 1 0 0 0 From positions 1, 2 and 4 of the leg ring the conductors are each connected to an individual grid of a different one of the cathode follower triodes, each such triode being one of a different assembly. From positions 3, 5 and 6 of the leg ring each conductor 25 controls two cathode followers, these being of the assemblies where the digit out is 1 for these leg ring positions. Position 7 is represented by a conductor 25 which is connected to grids of three different cathode follower triodes each in a different assembly. Conductor 25 from the #8 position of the leg ring is carried to the grid of a triode in a fourth matrix assembly which is of the type shown in FIG. 3, but has a fourth triode with its anode connected in parallel with thos of triodes 301, 302 and 303.

Now picture this fourth matrix as having its triodes 301, 302, and 303 subject to control by output potentials from the three cathode follower assemblies respectively. Also the fourth triode in this fourth matrix is directly controlled by the signal coming through conductor 25 from the #8 position of the leg ring. This matrix, then serves to translate a pulse representing the #8 position into a code combination representing the binary number 1000 and in distinction from binary number 000. The comparator unit 23 must make this distinction because the counting pulses registered in the synchronous pulse counter 24 start with 001 and end with 000 subsequent to 111. On the other hand, the reset condition of the leg ring 32 is one in which there is no potential applied to any of its output conductors 25. The cathode follower assemblies of th matrix 30, considering their integrated output, deliver on their three output circuits negative signal potentials which match the code pattern for 000 at the time when the counter 24 has reached its #8 count. These negative pulses are also carried to three of the triodes in the fourth matrix, the fourth triode being driven conductive by the pulse on conductor 25,; (during leg selecting position #8). Hence the interconnected anodes of the four triodes will be held at low potential for the eight leg address selection. During each of the other leg address selections at least one, of the cathode follower assemblies will have a output potential that will be applied to a grid or grids of tubes 301, 302 and 303, and so will be effective in holding the interconnected anodes of these triodes at low potential. These triodes and the fourth triode above mentioned have their anodes coupled to the grid of an inverter tube the anode of which is connected through a conductor 60 to a common line 61 which carries sampling pulses from comparators 18 and 23 to the joint control lock 33 (FIGS. 1 and 2). Line 61 must be held positive in order to release the lock 33.

The comparators 18 and 23 and the fourth matrix assembly in component 30 are cooperative in carrying out this requirement. During the reset interval of the leg ring, however, all four of the triodes of the fourth matrix will be held non-conductive, and, hence, the inverter tube which is controlled thereby will deliver a low output potential on conductor 60 and will prevent the release of lock 33 at a time when no address sampling is wanted.

The composition of different code patterns by the three basic cathode follower assemblies of the encoding matrix 30 will be well understood by those familiar with conventional matrix techniques. The three conductors 29 (FIG. 1) leading to the comparator 23 carry the encoded pattern of and potentials to comparator circuits of well known type. These same circuits are also fed with the changing patterns of the binary digit counts supplied by the counter 24, as previously described. When the two patterns become matched conductor 61 delivers the needed signal for releasing the lock 33.

THE COMPUTER 42 This computer is of a type which handles binary numbers under control of static pulses. All of the digits of a binary number are represented by circuit arrangements, one digit order of which is illustratively shown in FIG. 8.

This computer is adapted to add two binary numbers and also to subtract by adding the complement of the subtrahend. A subtractive operation is, therefore, equivalent to addition.

In order to show how the computer component 42 (FIG. 2) fits into the general scheme of the entire reservations system, We have indicated input conductors B (FIGS. 7 and 8) as going into each of seven different digital stage units of the computer 42 and carrying from the seven gated registers 40 a signal representing the value or 1 with respect to each denominational order of a seven digit binary number as read out from any section of the leg inventories. It will be recalled that the readout operation is simultaneous for all seven digits and the read-out of a particular inventory item is determined by the functioning of the comparator 39, which responds to the selection by the leg address of any particular leg inventory. Thus, the leg inventory balance becomes stored in the unit 40 and each digital order of the binary number representing that balance is fed with either a ground potential pulse representing the digit 1 or a negative pulse representing the digit 0. These pulses are all applied to terminals B in the different stages of the computer, one stage of which is shown in FIG. 8.

From the keyset, signals are transmitted through cable 8 and individually on seven different wires 53 representing the binary number value of a demand for seats. When an availability order is to be filled, the seat demand represents a number to be subtracted from the inventory balance. The different digit components of the computer 4 are each fed with one or the other of the two input potenby an explanation of the use of the entire computer in carrying out diiferent types of orders.

The components of one stage include six pentode tubes, U, V, W, Y, and Z. Two twin triode tubes E and F are also used. The usual positive and negative voltage supplies, together with an intermediate ground connection, are shown and are so familiar to those skilled in the art that their connections with various resistors of the input and output circuits would seem to require no further explanation. The pair of tubes U and V is so interconnected that variations of screen grid potential of one tube will alfect the bias on the suppressor grid of the other. The same is true of the pair of tubes W and X.

The pentode tube Y has its first grid subject to control by variations of suppressor grid potential in the tube U which, in turn, is subject to control by the screen grid in tube V. Furthermore, the bias on the suppressor grid of tube Y is held the same as that in tube V, which results from variations in screen grid potential in tube U.

In a similar manner, tube Z is made subject to control by variations of screen grid potentials in tubes W and X respectively.

The right hand section of tube E is a cathode follower triode, the output circuit from which supplies static potentials for the duration of a signalling interval representing the carry-out pulse C The left hand triode section of tube E is connected effectively as a diode and its function is merely to limit the range of grid bias potential appliedto the right hand section of the same tube E.

Tube F is similarly constituted with respect to tube E. Its right hand section is a cathode follower which delivers an output potential S representing the sum B+D+C as a units order digit irrespective of a carry to higher order.

There are eight permutations of potentials (input digit signals) as applied to terminals B, D and C simultaneously. The following table indicates the responses in the several tubes and at junction point A for each of the eight permutations. Ground potential applied to an input terminal or delivered by the cathode of a tube such as E or F represents binary numeral 1. A negative potential of, say, 30 volts represents "0. Screen grid (86) and anode potentials are indicated as Low (L) or High (H) according to conductance or cut-off conditions of the pentode tubes, and the eiiects of these variations are obvious to those skilled in the art.

Input Signals Tube U Tube V P Tube W Tube X Anodes Catho des oint A B D or so Anode so Anode so An. so A11. Y a g 0 0 0 H H H H H L L H L D t] 0 0 1 H H H H H L H L H L 0 1 0 1 0 H L L L H H H H L 0 l 0 1 1 H L L L H L L H H 1 (l 1 0 0 L L H L H H H H L 0 1 1 0 1 L L H L H L L H H 1 t) 1 1 0 L H L H H L L H H H 1 0 1 1 1 L H L H H L H L H H H l 1 *Means that the tube is non-conductive but the anode potential is low on account of the conductwo state in the other tube of the pair.

tials (ground or 30 volts) by which the digits of the seat demand number are represented. These potentials are applied at terminals D.

Each digital order component of the computer is also provided with a carry in terminal C As shown in FIG. 7, the digital orders are interconnected from stage to stage by means of these carry input circuits. Even the lowest order 2 is also provided with a so-called endaround-carry circuit C the control of which is unconventional, as will presently be explained. There is also a carry-out circuit C and a digitout circuit S for each of the denominational order sections of the computer.

The detailed explanation of the electronic circuit, as

EQUIPMENT FOR ENABLING THE COMPUTER TO EXECUTE DIFFERENT ORDERS The computer 42 is required to operate in different ways according to the instructions given to it for the execution of diiferent orders. Among the different types shown in FIG. 8, will now be given, and will be followed of orders enumerated in the early part of the specification 

19. A RUNNING INVENTORY SYSTEM COMPRISING SIGNAL STORAGE EQUIPMENT HAVING STORAGE SECTIONS FOR STORING CODE SIGNALS RESPECTIVELY REPRESENTING THE CURRENT NUMERICAL QUANTITATIVE VALUES OF A NUMBER OF DIFFERENT INVENTORY ITEMS, AND IN WHICH SAID CODE SIGNALS ARE SELECTABLE IN DIFFERENT COMBINATIONS TO FORM VARIABLE GROUPS OF INVENTORY ITEMS WHICH RESPECTIVELY COMPRISE DIFFERENT WORDS OF INFORMATION, SAID STORAGE EQUIPMENT HAVING A PLURALITY OF OTHER STORAGE SECTIONS FOR STORING DIFFERENT PREDETERMINED GROUPS OF ADDRESS SIGNALS RESPECTIVELY REPRESENTING THE LOCATION OF A PLURALITY OF CODE SIGNALS REPRESENTING MEMORY ITEMS IN DIFFERENT VARIABLE GROUPS THEREOF, A CALLING STATION HAVING MEANS FOR PRODUCING AND TRANSMITTING MESSAGES EACH INCLUDING A GROUPING CODE SIGNAL FOR SELECTING A PREDETERMINED GROUP OF SAID ADDRESS SIGNALS AND A SIGNAL REPRESENTING A DESIRED QUANTITY OF EACH OF THE INVENTORY ITEMS OF THE SELECTED GROUP, MEANS ASSOCIATED WITH SAID SIGNAL STORAGE EQUIPMENT FOR TEMPORARILY STORING THE SIGNALS OF EACH INCOMING MESSAGE, MEANS INCLUDING RECORDING AND READ-OUT DEVICES FOR SCANNING SAID STORAGE SECTIONS IN CONTINUOUS SUCCESSION, MEANS INCLUDING ADDRESS SELECTION CIRCUITS CONTROLLED BY SAID STORED GROUPING SIGNAL FOR LOCATING AND READING OUT FROM THE ADDRESS STORAGE SECTION SIGNALS REPRESENTING THE ADDRESSES OF THE CODE SIGNALS REPRESENTING INVENTORY ITEMS COMPRISING THE PREDETERMINED GROUP, MEANS FOR TEMPORARILY STORING THE ITEM ADDRESS SIGNALS AS THEY ARE READ OUT, INVENTORY ITEM SELECTION AND READ-OUT CIRCUITS CONTROLLED BY SAID TEMPORARILY STORED ITEM ADDRESS SIGNALS FOR LOCATING AND READING OUT FROM SAID DATA STORAGE SECTIONS CODE SIGNALS REPRESENTING THE CURRENTLY STORED INVENTORY VALUES OF THE CORRESPONDING ITEMS, MEANS FOR TEMPORARILY STORING SAID INVENTORY SIGNALS THUS READ OUT, MEANS INCLUDING A COMPUTER JOINTLY CONTROLLED BY EACH OF THE LAST NAMED SIGNALS AND THE SIGNAL REPRESENTING SAID DESIRED QUANTITY IN THE INCOMING MESSAGE FOR DETERMINING IN SUCCESSION WHETHER THE CURRENTLY STORED INVENTORY VALUE OF EACH OF SAID ITEMS OF THE SELECTED GROUP IS AT LEAST EQUAL TO SAID DESIRED QUANTITY OR IS LESS THAN SAID DESIRED QUANTITY, AND MEANS CONTROLLED IN ACCORDANCE WITH THE RESULTS OBTAINED BY SAID COMPUTER FOR INDICATING AT THE CALLING STATION WHETHER SAID INVENTORY VALUES OF THE ITEMS OF THE GROUP EITHER ARE SUFFICIENT OR ARE INSUFFICIENT TO SUPPLY THE DESIRED QUANTITY SPECIFIED IN THE MESSAGE. 